Object disappearing and origin points
If you want to display or edit your mesh the way you see in Object Mode but after using modifiers, be sure to select those options (green one for displaying, red for editing) for all modifiers:


What's happening is that the modifiers are not set to display in Edit mode, so when you press Tab you'll get the "original" mesh, without any modifications (in your .blend, for example, you can still see a small piece of your track  in Edit mode).
Also, when you press Tab with nothing selected, Blender will enter Edit mode for the active object (the one with yellowish origin), even if it's not selected. So, probably your track is the active object when you deselect everything.